The present invention relates to a print control apparatus, or more in particular to a print image data storage system capable of efficiently using a full-dot memory for storing a page image data in a print control apparatus.
A printing apparatus for preparing a one-dot one-bit print image data from a print data expressed in a plurality of dots and transferring a prepared image data to a printing mechanism to produce a print is comprised of a page memory for forming an image data corresponding to the print image. The page memory is used to store an image data covering one page of print unit and is also called a full-dot memory. An image data to be printed is developed in a full-dot memory.
The full-dot memory normally has an address (x, y) of a two-dimensional coordinate corresponding to a dot coordinate in order to attain correspondence to a two-dimensional print image. This address is designated by two registers for x and y register addresses.
There are two page print forms: One is a portrait (longitudinal) 22 shown in FIG. 1B, and the other a landscape (lateral) 21 shown in FIG. 1A. A print image data, if to be adaptable for both of the print forms, is required to be developed in a full-dot memory 10 regardless of the direction of the page data. It is also necessary that image data of variously different sized sheets can be developed in the full-dot memory.
In the case of storing a print area of 400 dpi (dots/inch), A3 size (11.7".times.16.5") in the full-dot memory 10, for example, bits in the number of 16.5.times.400 which is equivalent to 825 bytes are required along the lateral direction of the raster in order to accommodate an area of a landscape (11.7" by 16.5"). Assuming an X address register of one word (four bytes), a maximum of 207 (=825+4) words are available for each row. An 8-bit word address register is therefore necessary for the X direction. If each bit position of 16.5.times.400 bits is to be designated directly, on the other hand, 13-bit addresses are required. In the longitudinal direction, a raster in the number of 16.5.times.400 (=6,600) (the number of bits in the longitudinal direction) are necessary to accommodate a portrait area (16.5" by 11.7"). A 13-bit register is used as a y address register for designating a raster in the longitudinal direction.
FIG. 2 is a diagram illustrating a memory map with a segment configuration of a two-dimensional full-dot memory. To facilitate the understanding, explanation will be made first about the case in which a page of area is set by a two-dimensional address. A one-page area for storing a print image data is set in an area 20 of full-dot memory on one segment. As shown in FIG. 2, for example, an area for accommodating a landscape 21 or an area for accommodating a portrait 22 by a two-dimensional address is set in the area 20 on a segment of the full-dot memory. The diagram represents an area accommodating an A3-sized landscape 21 by a two-dimensional address (x, y) and an area accommodating an A3-sized portrait 22 by a two-dimensional address (x, y).
In the case where the area 20 on one segment of a full-dot memory is set by a two-dimensional address in this way, it is necessary to configure both lateral and longitudinal directions to 8,192 dots, i.e., to the capacity with the length of 20.48" for each direction. If an area 20 on one segment of a full-dot memory is configured of two-dimensional addresses representing 8,192 bits for both lateral and longitudinal directions in this way, a 13-bit address is involved for both x and y addresses. If one dot is made to correspond to one bit of memory and the A3-sized sheet to both the landscape and portrait, therefore, a capacity of 8 MB is required for one segment of a full-dot memory in the case of a two-dimensional address (x, y).
On the other hand, the amount of bits of an A3-sized sheet is 3.86 MB for 400 bpi regardless of landscape or portrait. As a result, only 3.86 MB out of the capacity 8 MB of the full-dot memory is consumed, while the remaining approximately half memory capacity is left unused. In other words, the hatched portions of FIGS. 1A and 1B are not used.
As described above, if a full-dot memory is allotted directly to a two-dimensional address (x, y), the effective use of a memory is impossible although the access rate is advantageously improved. Especially when storing a multiplicity of pages in a full-dot memory for a two side printer, a high definition of 600 to 1000 dpi in print dot density leads to a very large capacity of the full-dot memory.
An example of a print control apparatus and a memory control using a two-dimensional full-dot memory as described above are disclosed in JP-A-61-75424 and JP-A-60-209880.